Methods and arrangements for processing of measurement data in cellular communication systems

ABSTRACT

The problem of unsynchronized internal clocks of user equipments in a cellular communication system is addressed by a solution where a mechanism relying on a standalone clock function in user equipments is provided. Embodiments provide a network node that distributes a time reference to a user equipment (UE), and wherein the UE, using an internal clock function, time-stamps the logged measurements and/or events relative to the received time reference. When the UE has logged measurements the UE indicates to the network node that it has an available measurement log. The network node may then request several UEs to deliver their measurement log, respectively. The network node is then able to retrieve time stamped measurement information from the measurement log of each UE relative the sent time reference. Furthermore, the network node is then able to compare measurement information from each UE in a cell provided at the same time interval in all UEs.

TECHNICAL FIELD

The present invention relates to processing of measurement data. Moreparticularly, the present invention relates to arrangements and methodsfor processing of measurement data in a user equipment and a networknode comprised in a cellular communication system.

BACKGROUND

For next generation of mobile telecommunications systems 3^(rd)Generation Partnership Project (3GPP) is in the process of definingsolutions for user equipment (UE) measurement logging function andimmediate reporting function called Minimization of the Drive Tests(MDT). The MDT study aims at assessing the feasibility, benefits andcomplexity of automating the collection of UE measurements to minimizethe need of manual drive-tests. The work under the MDT study shoulddefine use cases and requirements for minimizing drive-tests in nextgeneration LTE/HSPA networks. Also, based on the defined use cases andrequirements, the MDT should focus on study the necessity of definingnew UE measurements logging and reporting capabilities for minimizingdrive tests and analyze the impact on the UE.

The use cases for the MDT will be given as following.

-   -   Radio coverage optimization    -   Mobility optimization    -   Network capacity optimization    -   Parameterization for common channels    -   Quality of Service verification

1. Radio coverage optimization; that is, information about radiocoverage is essential for network planning, network optimization andRadio Resource Management (RRM) parameter optimization (e.g. idle modemobility parameter setting, common channel parameterization), as well asbackend network management activities, such as network dimensioning,CAPEX/OPEX planning and marketing. Additionally the detection ofcoverage problems (e.g. coverage holes, pilot pollution, low userthroughput, etc.) in specific areas may be performed.

2. Mobility optimization; that is, mobility optimization is an importantpart of network operation. Information about mobility problems orfailures can be used to identify localized lack of coverage or the needto adapt the network parameters setting, (e.g. in order to avoid tooearly or too late handover and to improve the handover success rate andoverall network performance)

3. Network capacity optimization; that is, the operator may need to beable to determine if there is too much/little capacity in certain partsof the network. Such determination may help to determine placement ofnew cells, to configure common channels and to optimize other capacityrelated network parameters.

4. Parameterization for common channels; that is, user experience and/ornetwork performance can be degraded by suboptimal configuration ofcommon channels (e.g. random access, paging and broadcast channels).Detecting problems (e.g. on UL or DL common channel coverage) oranalyzing the performance (e.g. connection setup delay) for theprocedures associated with common channels, may help network parametersetting and configuration change for system performance optimization.

5. Quality of Service verification; that is, one of the objectives ofthe network performance analysis is the verification of the quality ofservice (e.g. user throughput). This may also allow detecting criticalconditions and determining the need to change the network configuration,parameter settings or capacity extension.

In the following, UE measurement logs for minimizing drive tests will bedescribed. The measurement logs may be taken at the occurrence ofpredefined “triggers”, e.g. periodic trigger, a failure event. Thefollowing UE measurements (or similar functionality) are considered forUE-internal logging:

1. Periodical downlink pilot signal strength/quality measurements ofserving cell and neighbour cells on same and other radio accesstechnologies.

2. Serving cell becomes worse than threshold; that is, radio environmentmeasurements are logged when the serving cell metric becomes worse thanthe configured threshold.

3. Transmit power headroom becomes less than threshold; that is,transmit power headroom and radio environment measurements are loggedwhen UE transmit power headroom becomes less than the configuredthreshold.

4. Random access failure; that is, details on the random access andradio environment measurements are logged when a random access failureoccurs.

5. Paging channel failure; that is, details of the radio environment,location, time and cell identity are logged at the point when the UEfails to decode the PCCH on the Paging channel for two consecutivetimes.

6. Broadcast channel failure; that is, details of the radio environment,location, time, cell identity and frequency are logged at the point whenthe UE fails to read the relevant DL common channels to acquire requiredsystem information for camping on a cell.

7. Radio link failure report; that is, radio measurements available atthe UE are reported at the RLF occurrence.

The network can request the UE to perform logging of measurements. TheUE executes measurements (e.g. periodical downlink pilot measurements)and logs these measurements internally in a sequential manner.Typically, the log stored internally in the UE will contain e.g. somehour of logged measurement information. For post-processing purpose,these logged measurements/events may be tagged with time information(e.g., time stamps).

When the UE has logged measurements the UE indicates to the network thatit has an available measurement log. The network may then request the UEto deliver the measurement log. This procedure is illustrated in FIG. 1.The UE sends 10 an indication to a network node, e.g. an eNodeB or a RNC(Radio Network Controller), that it has an available measurement log.The network node then determines 11 whether is wants to request themeasurement log. If it determines to request the measurement log itsends 12 a request to the UE. Thereupon the UE delivers 13 themeasurement log to the network node.

The network collects measurement logs from several UEs in differentcells. By collecting and retrieving information from the measurementlogs the network is able to perform optimization of radio coverage,mobility, network capacity and to perform parameterization for commonchannels and verification of QoS.

It has been agreed upon to include a time stamping for the MDTmeasurements. However, the timestamp does not need to be very accurate.It is recognized that a simple mechanism is sufficient. For example,during a log activity of e.g. one hour, one can assume that a drift ofapproximately ±10 s is acceptable.

Solutions using Global Positioning System (GPS), as well as othernetwork-broadcast time-of-day information have been discussed. Amechanism that e.g. uses System Frame Number (SFN) of the current cellas timing source has the potential of providing a very accurate timereference. However, a UE will change cells and occasionally even losecell coverage causing problems with the time stamping during theperformance of UE measurement logging function.

Most user equipments are equipped with a clock. However, in many casesthe clocks of the user equipments are not synchronized with a commontime base, e.g. the local time. If the UE utilizes the internal clockwhen time stamping measurement data, problems will arise when thenetwork retrieves time stamped measurement information from themeasurement logs and compare the time stamp measurement information fromseveral UEs in a cell.

The document “Study on Minimization of drive-tests in Nest GenerationNetworks; (Release 9)”, 3^(rd) Generation Partnership Project; TechnicalSpecification Group Radio Access Network; 3GPP TR 36.805, V9.0.0, 21Dec. 2009, pages 1-24, discusses automating the collection of UEmeasurements, i.e. MDT, by executing measurements in the UE. It furtherdiscloses storing the measurements in a measurement log wherein themeasurements are linked to a time stamp that is available in the UE andreceiving a request to deliver the log in the UE. Thereupon the log isdelivered to the network node. However, the accuracy of the timeinformation is underdetermined.

The document “Time stamp achievement and reporting in MDT”, TD TECH,3GPP DRATFT; R2-102495, 4 Apr. 2010 relates to the issue of the accuracyof time information in MDT. It discusses a mechanism of reporting timestamp via RRC signalling. A relative time is used for the time stamp ofthe measurement in the UE. The relative time is linked to a counterwhich is turned on in the UE when measurement is triggered. However, thenetwork node does not know the accuracy of the time information in thelog.

The document “Logged MDT principles”, NOKIA SIEMENS NETWORKS et al, 3GPPDRAFT; R2-103191, 4 May 2010 relates to configuration and reporting of ameasurement log for MDT but does not mention the accuracy of the timeinformation.

SUMMARY

The object of the present invention is to address some of the problemsand disadvantages outlined above, and to provide methods andarrangements that enable processing of measurement data in a cellularcommunication system.

The above stated object is achieved by means of the methods and thearrangements according to the independent claims.

In accordance with a first aspect of embodiments, a method in a userequipment for enabling processing of measurement data is provided. Theuser equipment is configured to communicate with a network nodecomprised in a cellular communication system. The user equipmentcomprises a measurement log for storing measurement data and timereference information. Furthermore, the method comprising receiving atime reference from the network node. Moreover, an internal clockfunction is started at the reception of the time reference. One or moremeasurement is then executed and measurement data is stored with adetermined value of the internal clock function in the measurement log.Furthermore, the method comprising sending an indication to the networknode that the measurement log is available. A request to deliver themeasurement log is received from the network node. Finally, the methodcomprising delivering the measurement log to the network node.

In accordance with a second aspect of embodiments, a user equipment forenabling processing of measurement data is provided. The user equipmentis configured to communicate with a network node comprised in a cellularcommunication system. The user equipment comprises a storage unit forstoring a measurement log in which measurement data and time referenceinformation are stored. The user equipment further comprises atransceiver adapted to receive a time reference from the network nodeand a processor unit adapted to start an internal clock function whenthe time reference is received, execute a measurement, and store themeasurement data with a determined value of the internal clock functionin the measurement log. Moreover, the transceiver is further adapted tosend an indication to the network node that the measurement log isavailable and to receive a request to deliver the measurement log fromthe network node and thereupon to deliver the measurement log to thenetwork node.

In accordance with a third aspect of embodiments, a method in a networknode for processing of measurement data is provided. The network node iscomprised in a cellular communication system and configured tocommunicate with at least two user equipments. The method comprising,for each user equipment, sending a time reference to the user equipment.Furthermore, the method comprising receiving an indication from the userequipment that a measurement log is available and sending a request todeliver the measurement log to the user equipment. Moreover, the methodcomprising receiving the measurement log from the user equipment andcomparing the measurement logs of at least two user equipments bycomparing measurement data logged at a value of time of an internalclock function of the respective user equipment with respect to the senttime references.

In accordance with a fourth aspect of embodiments, a network node forprocessing of measurement data is provided. The network node iscomprised in a cellular communication system and configured tocommunicate with at least two user equipments. The network nodecomprises a transceiver adapted to, for each user equipment, send a timereference to the user equipment and to receive an indication from theuser equipment that a measurement log is available. The transceiver isfurther adapted to send a request to deliver the measurement log to theuser equipment and to receive the measurement log from the userequipment. The network node further comprises a processor unit adaptedto compare the measurement logs of at least two user equipments bycomparing measurement data logged at a value of time of an internalclock function of the respective user equipment with respect to the senttime references.

An advantage of particular embodiments is that they provide a solutionto the stated object which offers simple implementation and operationalsimplicity without requiring complex arrangements in the user equipmentor in the network.

A further advantage of particular embodiments is that they provide asolution which does not require synchronization of clocks in the userequipment and the network.

Further advantages and features of embodiments will become apparent whenreading the following detailed description in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding, reference is made to the following drawingsand preferred embodiments.

FIG. 1 illustrates the prior art procedure of reporting of themeasurement log from the user equipment to the network.

FIG. 2 shows an exemplary embodiment of a structure of the userequipment measurement log stored internally in the user equipment andreported to the network node.

FIG. 3 shows a flowchart of an exemplary embodiment of a method in auser equipment for enabling processing of measurement data.

FIG. 4 shows a flowchart of an exemplary embodiment of a method in anetwork node for processing of measurement data.

FIG. 5 is a block diagram illustrating the user equipment and thenetwork node according to embodiments.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth, such as particular sequencesof steps and particular device configurations in order to provide athorough understanding of the embodiments. It will be apparent to oneskilled in the art that the embodiments may be practised in otherembodiments that depart from these specific details. In the drawings,like reference signs refer to like elements.

Moreover, those skilled in the art will appreciate that the means andfunctions explained herein below may be implemented using softwarefunctioning in conjunction with a programmed microprocessor or generalpurpose computer, and/or using an application specific integratedcircuit (ASIC). It will also be appreciated that while the currentinvention is primarily described in the form of methods and devices, theinvention may also be embodied in a computer program product as well asa system comprising a computer processor and a memory coupled to theprocessor, wherein the memory is encoded with one or more programs thatmay perform the functions disclosed herein.

Embodiments are described herein by way of reference to particularexample scenarios. Particular aspects are described in a non-limitinggeneral context in relation to an LTE system. It should though be notedthat the invention and its exemplary embodiments may also be applied toother types of radio access networks for processing measurement data.

In the following detailed description a number of embodiments aredisclosed wherein the problem of unsynchronized internal clocks of userequipments in a cellular communication system is addressed by a solutionwhere a mechanism relying on a standalone clock function in userequipments is provided. Embodiments described in more detail in thefollowing provide a network node that distributes a time reference to auser equipment (UE), and wherein the UE, using an internal clockfunction, time-stamps the logged measurements and/or events relative tothe received time reference. When the UE has logged measurements the UEindicates to the network node that it has an available measurement log.The network node may then request several UEs to deliver theirmeasurement log, respectively. The network node is then able to retrievetime stamped measurement information from the measurement log of each UErelative the sent time reference. Furthermore, the network node is thenable to compare measurement information from each UE in a cell providedat the same time interval in all UEs.

According to one exemplary embodiment, a network node comprised in acellular communication system, e.g. a LTE system, communicates with UEsin a serving cell. The network node sends a time reference to a UE. Forexample, the network node could include the time reference in a MDT(Minimization of the Drive Tests) measurement configuration message sentto the UE when the network requests the UE to perform logging ofmeasurements. The time reference could e.g. be a time-of-day and dateindication. The exact content does not need not be standardized, and caninstead be left for the choice of the operator of the cellularcommunication system. Furthermore, at reception of the MDT measurementconfiguration message including the time reference, the UE starts aninternal clock function or a clock counter from zero, and steps it e.g.by one every second. The UE additionally stores the time reference inthe measurement log. Thereupon the UE is able to “timestamp” eachsubsequently logged MDT measurement with the current value of theinternal clock function, and adds this to the measurement log.

FIG. 2 illustrates an exemplary embodiment of a structure of themeasurement log stored internally in the UE and reported to the networknode, including measurement and time information. The measurement log 20comprises the time reference Initial MDT Time Ref 21 received from thenetwork node. It further comprises a first MDT measurement 22 which istimestamped i.e. the MDT measurement is stored in the log with thecurrent value of the internal clock function MDT_TIME at the time ofmeasuring. The measurement log also comprises a second MDT measurement23 which is timestamped in the same manner. The log may include severaltimestamped MDT measurements 24 as illustrated in FIG. 2. Typically, themeasurement log will include e.g. some hour of logged measurementinformation.

In FIG. 3 an exemplary embodiment of a method in a UE for enablingprocessing of measurement data is illustrated. The UE is configured tocommunicate with a network node comprised in a cellular communicationsystem. In a first step 30 the UE receives a time reference T_(ref) fromthe network node. The time reference may be included in the same messagewhich is sent to the UE from the network node requesting the UE to startlogging measurements such as the MDT measurement configuration message.Then in a next step 31, the UE starts an internal clock function T_(int)upon the reception of the time reference T_(ref). The UE startsexecuting measurements in the cell in a further step 32. The measurementmay be any of the measurements required for MDT functionality. Forexample, the measurement executed may be a downlink pilot signalstrength measurement of serving or neighbour cell. It may also be adownlink pilot signal quality measurement of serving or neighbour cell.It should be noted that the measurements could be executed periodicallyin the UE. When the measurement is executed the UE stores 33 themeasurement data in a measurement log in the UE. The measurement data isstored with a current value of the internal clock function T_(int) inthe measurement log i.e. the measurement data is stored with a timestampin the log. The UE sends 34 an indication to the network node that themeasurement log is available. In a further step 35 the UE receives arequest from the network node to deliver the measurement log to thenetwork node. The UE then delivers 26 the measurement log comprising thetimestamped measurement data and the time reference T_(ref) to thenetwork node.

In FIG. 4 an exemplary embodiment of a method in a network node forprocessing of measurement data is illustrated. The network node iscomprised in a cellular communication system and configured tocommunicate with at least two user equipments in a cell which is servedby the network node. In a first step 40 the network node sends a timereference T_(ref) to each UE. The time reference T_(ref) may be includedin the same message which is sent to the UE requesting the UE to startlogging measurements, such as the MDT measurement configuration message.The UE will start logging measurement data in a measurement log inaccordance with the previously described method. In a further step 41 anindication is received from the UE that a measurement log is availablein the UE. Next, the network node sends 42 a request to deliver themeasurement log to the UE. The network node receives the measurement login a further step 43. Upon the reception of measurement logs of at leasttwo UEs the network node can compare 44 the measurement logs. This stepis performed by comparing measurement data logged at a value of time ofan internal clock function of the respective user equipment with respectto the time references T_(ref) sent to each UE, respectively.

FIG. 5 is a schematic block diagram schematically illustrating anexemplary UE 510 that is configured to communicate with an exemplarynetwork node 520 comprised in a cellular communication system. The UE510 and network node 520 can be implemented using various components,both hardware and software. It should be noted that the network node mayserve several UEs. However, for simplicity reasons only one UE isillustrated in the figure.

For example, as shown generally in FIG. 5, such a UE 510 include aprocessor unit 512, one or more storage devices 514, an operating system(not shown) running on the processor unit 512 as well as a correspondingapplication, e.g., an application which processes measurement data inthe manner described above. Additionally, such a network node 520include a processor unit 522, one or more storage units 524, anoperating system (not shown) running on the processor unit 522 as wellas a corresponding application, e.g., an application which processesmeasurement data in the manner described above. Both the UE 510 and thenetwork node 520 may comprise an interface unit 516, 526 to facilitatecommunications between the UE 510 and the network node 520. For example,the interface unit 516, 526 may include a transceiver capable ofcommunicating wirelessly over an air interface, e.g., as specified byLTE, including hardware and software capable of performing the necessarymodulating, coding, filtering and the like, as well as demodulating anddecoding to process such signals.

The transceiver unit 518 comprised in the UE 510 is adapted to receive atime reference T_(ref) from the network node 520. The processor unit 512is adapted to store the received time reference T_(ref) in a measurementlog which may be comprised in the storage unit 514. The processor unit512 is further adapted to start an internal clock function whenreceiving the time reference T_(ref) from the network node 520.Furthermore, the processor unit 512 is adapted to execute measurementsin the cell and to store the measurement data with a determined value ofthe internal clock function in the measurement log comprised in thestorage unit 514. The transceiver 518 is adapted to send an indicationto the network node 520 that the measurement log is available and toreceive a request to deliver the measurement log from the network node520. Finally, the transceiver 518 comprised in the UE 510 is furtheradapted to deliver the measurement log to the network node 520.

Moreover, the transceiver 528 comprised in the network node 520 isadapted to send a time reference T_(ref) to the UE 510. It is furtheradapted to receive an indication from the UE 510 that a measurement logis available. The transceiver 528 is also adapted to send a request todeliver the measurement log to the UE 510 and then to receive themeasurement log from the same. The processor unit 522 comprised in thenetwork node 520 is adapted to then compare the measurement logs of atleast two user equipments 510 by comparing measurement data logged at avalue of time of an internal clock function of the respective userequipment 510 with respect to the sent time references T_(ref).

The embodiments may, of course, be carried out in other ways than thosespecifically set forth herein without departing from essentialcharacteristics of the embodiments described. The present embodimentsare to be considered in all respects as illustrative and notrestrictive.

The invention claimed is:
 1. A method in a user equipment for enablingprocessing of measurement data, the user equipment configured tocommunicate with a network node in a cellular communication system, theuser equipment having a measurement log for storing measurement data andtime reference information, the method comprising: receiving a timereference from the network node; starting an internal clock at thereception of the time reference; storing the time reference in themeasurement log; sending an indication to the network node that themeasurement log is available; executing one or more measurements;storing measurement data from the measurements with a determined valueof the internal clock in the measurement log, the determined value ofthe internal clock being an amount of time elapsed relative to the timereference received; receiving a request to deliver the measurement logfrom the network node; delivering the measurement log to the networknode.
 2. The method of claim 1, wherein the internal clock is a counter.3. The method of claim 2, wherein the counter is stepped one step byevery second.
 4. The method of claim 1, wherein the time reference is atime-of-day and date indication.
 5. The method of claim 1, wherein theexecuting one or measurements is performed periodically.
 6. The methodof claim 1, wherein the measurement is a downlink pilot signal strengthmeasurement of serving cell or neighbor cell.
 7. The method of claim 1,wherein the measurement is a downlink pilot signal quality measurementof serving cell or neighbor cell.
 8. A user equipment for enablingprocessing of measurement data, the user equipment configured tocommunicate with a network node in a cellular communication system, theuser equipment comprising: a storage device configured to store ameasurement log in which measurement data and time reference informationare stored; a processor circuit configured to: start an internal clockwhen a time reference is received; store the time reference in themeasurement log; execute a measurement; and store the measurement datawith a determined value of an internal clock in the measurement log, thedetermined value of the internal clock being an amount of time elapsedrelative to the time reference; a transceiver configured to: send anindication to the network node that the measurement log is available;receive the time reference from the network node; receive a request todeliver the measurement log from the network node; deliver themeasurement log to the network node.
 9. The user equipment of claim 8,wherein the internal clock is a counter.
 10. The user equipment of claim9, wherein the counter is stepped one step by every second.
 11. The userequipment of claim 8, wherein the time reference is a time-of-day anddate indication.
 12. The user equipment of claim 8, wherein theprocessor circuit is configured to execute the measurement periodically.13. The user equipment of claim 8, wherein the measurement is a downlinkpilot signal strength measurement of serving cell or neighbor cell. 14.The user equipment of claim 8, wherein the measurement is a downlinkpilot signal quality measurement of serving cell or neighbor cell.
 15. Amethod, in a network node, for processing of measurement data, thenetwork node being in a cellular communication system and configured tocommunicate with user equipment, the method comprising: for two or moreuser equipment: sending a time reference to the user equipment;receiving an indication from the user equipment that a measurement logis available; sending a request, to the user equipment, to deliver themeasurement log; receiving the measurement log from the user equipment;comparing the measurement logs of at least two of the two or more userequipment by comparing measurement data having been logged withcorresponding values of an internal clock of the respective userequipment, the corresponding values of the internal clocks being a timeelapsed relative to the time references sent to the respective userequipment.
 16. The method of claim 15, wherein at least one of the senttime references is a time-of-day and date indication.
 17. The method ofclaim 15, wherein the measurement logs comprise downlink pilot signalstrength measurements of served cell or neighbor cell.
 18. The method ofclaim 15, wherein the measurement logs comprise downlink pilot signalquality measurements of served cell or neighbor cell.
 19. A network nodefor processing of measurement data, the network node being in a cellularcommunication system and configured to communicate with user equipment,the network node comprising: a transceiver configured to, for two ormore user equipment: receive an indication from the user equipment thata measurement log is available; send a time reference to the userequipment; send a request to deliver the measurement log to the userequipment; receive the measurement log from the user equipment; aprocessor circuit configured to compare the measurement logs of at leasttwo of the two or more user equipment by comparing measurement datahaving been logged with corresponding values of an internal clock of therespective user equipment, the corresponding values of the internalclocks being a time elapsed relative to the time references sent to therespective user equipment.
 20. The network node of claim 19, wherein atleast one of the sent time references is a time-of-day and dateindication.
 21. The network node of claim 19, wherein the measurementlogs comprise downlink pilot signal strength measurements of served cellor neighbor cell.
 22. The network node of claim 19, wherein themeasurement logs comprise downlink pilot signal quality measurements ofserved cell or neighbor cell.